1. Technical Field
The present invention relates to a linear motion hydrostatic bearing assembly and, more particularly, to a self-compensating linear motion hydrostatic bearing assembly having a manifold which interconnects spaced bearing races of the bearing assembly to compensate for loading of the bearing assembly.
2. Background of Related Art
Linear motion hydrostatic bearings are well known and have been used for many years for the near frictionless movement of masses. Hydrostatic bearings are characterized as having excellent low friction, accuracy, and repeatability characteristics, with a theoretically infinite life. Hydrostatic bearings also have excellent damping characteristics which result from hydrostatic fluid acting as a shock absorber between the apparatus to which the bearing is associated and an applied load.
Typically, hydrostatic bearings maintain the distance between a bearing race and a support rail by supplying a thin pressurized film of fluid into the gap between the bearing race and the support rail. One type of hydrostatic bearing is a self-compensating hydrostatic bearing. Self-compensating hydrostatic bearings respond automatically to a change in bearing gap by changing the flow of fluid to pockets positioned along the bearing races.
U.S. Pat. No. 5,104,237 ("Slocum") discloses a self-compensating hydrostatic bearing for supporting a bearing carriage along a bearing rail. Slocum's hydrostatic bearing includes geometrically opposed pockets formed in the bearing carriage surfaces facing the bearing rail and compensating units in fluid communication with each of the pockets. Each compensating unit includes an annulus and a hole positioned on the carriage surface. The hole is connected to a pocket positioned on the opposite side of the bearing carriage by a channel formed in the bearing carriage. A constant pressure source of fluid is connected to each annulus to supply fluid to the annulus, where it flows across the bearing gap into the hole and to the opposite side pocket. As a load is applied to the bearing carriage, the resistance of fluid exiting the bearing pocket on the load side increases while the resistance of fluid exiting the bearing pocket on the opposite side decreases. The pressure increases in the pocket on the load side until the differential pressure generated between the two pockets balances. Thus, self-compensation is provided.
Although Slocum's hydrostatic bearing provides self-compensation, the difficulties associated with machining the channels which connect the holes of the compensating units with the pockets positioned on opposite sides of the bearing carriage render the hydrostatic bearing difficult and costly to manufacture.
Accordingly, a need exists for an improved self-compensating hydrostatic bearing which has the ability to compensate for uneven loads and may be manufactured easily and cost effectively.